routing: Fix possible infinite loop on first hop misleading hint

Add ignore condition to additional edges that connect to self. These
edges are already known and avoiding these hints protect the payment
from malformed channel ids which could lead to infinite loop.

Fixes lightningnetwork#6169.

Co-authored-by: lsunsi <lsunsi@pm.me>

routing/integrated_routing_context_test.go

@@ -10,6 +10,7 @@ import (
 	"github.com/lightningnetwork/lnd/kvdb"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing/route"
+	"github.com/lightningnetwork/lnd/zpay32"
 )
 
 const (
@@ -47,6 +48,7 @@ type integratedRoutingContext struct {
 
 	mcCfg          MissionControlConfig
 	pathFindingCfg PathFindingConfig
+	routeHints     [][]zpay32.HopHint
 }
 
 // newIntegratedRoutingContext instantiates a new integrated routing test
@@ -177,6 +179,7 @@ func (c *integratedRoutingContext) testPayment(maxParts uint32,
 		Amount:         c.amt,
 		CltvLimit:      math.MaxUint32,
 		MaxParts:       maxParts,
+		RouteHints:     c.routeHints,
 	}
 
 	var paymentHash [32]byte